The present invention relates to a photosensor which detects light in an ultraviolet region and light in a visible light region respectively, and a photo IC equipped with the same.
A conventional ultraviolet sensor is provided wherein an “E”-shaped N-type high concentration diffusion layer with an N-type impurity diffused therein in a high concentration and a “π”-shaped P-type high concentration diffusion layer with a P-type impurity diffused therein in a high concentration are disposed, in a silicon semiconductor layer of a semiconductor substrate having an SOI (Silicon On Insulator) structure in which a silicon semiconductor layer having a thickness of 150 nm or so is formed on a silicon substrate with an embedded oxide film interposed therebetween, opposite to each other in engagement with each other with a silicon semiconductor layer with an N-type impurity diffused therein in a low concentration being interposed therebetween, and a depletion layer is formed in a lateral direction to form a lateral ultraviolet photosensitive element photosensitive only to light in an ultraviolet region, whereby the intensity of the light in the ultraviolet region is detected (refer to, for example, a patent document 1 (Japanese Patent Publication Laid Open Number Hei 7 (1995)-162024)).
As to a conventional visible light sensor, an N-type region is formed in a surface layer of a P-type silicon substrate and a P-type region is formed in a surface layer of the N-type region, a first visible light photosensitive element having peak sensitivity in a visible light region is formed by the N-type region and the P-type region, and a second visible light photosensitive element having peak sensitivity in an infrared region is formed by the P-type silicon substrate and an N-type region, thereby forming a vertical visible light sensor. Outputs produced from the first and second visible light photosensitive elements respectively are amplified and subjected to arithmetic processing thereby to detect the intensity of light in the visible light region (refer to, for example, a patent document 2 (Japanese Patent Publication Laid Open Number 2004-6694)).
However, each of the techniques of the patent documents 1 and 2 is accompanied by problems that since the ultraviolet sensor equipped with the ultraviolet photosensitive element and the visible light sensor equipped with the two visible light photosensitive elements are respectively formed singly, there is a need to mount separately-provided ultraviolet and visible light sensors to a wiring board or the like formed with a peripheral circuit thereby to form a photosensor for the purpose of forming a photosensor equipped with a function for detecting light in the ultraviolet region and a function for detecting light in the visible light region, thereby increasing the manufacturing cost and causing a need to ensure space for providing the wiring board at an apparatus equipped with the photosensor, thus encountering difficulties in miniaturizing an apparatus equipped with the photosensor including the function of detecting light in the ultraviolet region and the function of detecting light in the visible light region.